Thin Composite Carbon Molecular Sieve Membranes from a Polymer of Intrinsic Microporosity Precursor

Wojciech Ogieglo, Andreas Furchner, Xiaohua Ma, Khalid Hazazi, Abdulrahman Alhazmi, Ingo Pinnau

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Ultra-thin composite carbon molecular sieve (CMS) membranes were fabricated on well-defined inorganic alumina substrates using a polymer of intrinsic microporosity (PIM) polyimide as precursor. Details of the pyrolysis-related structural development were elucidated using focused-beam, interference-enhanced spectroscopic ellipsometry (both in the UV-VIS and IR range) which allowed accurate determination of the film thickness, optical properties as well as following the chemical transformations. The pyrolysis-induced collapse of thin and bulk PIM-derived CMS membranes was compared with CMS made from a well-known non-PIM precursor 6FDA-DABA. Significant differences between the PIM and non-PIM precursors were discovered and explained by a much larger possible volume contraction in the PIM. In spite of the differences, surprisingly, the gas separation properties did not fundamentally differ. The high temperature collapse of the initially amorphous and isotropic precursor structure was accompanied by a significant molecular orientation within the formed turbostratic carbon network guided by the laterally constraining presence of the substrate. This manifested itself in the development of uniaxial optical anisotropy, which was shown to correlate with increases in gas separation selectivity for multiple technologically important gas pairs. Reduction of CMS skin thickness significantly below ~1 micron induced large losses in permeability coefficients with only small to moderate effects on selectivity. Remarkably, skin thickness reduction and physical aging seemed to superimpose onto the same trend, which explains and strengthens some of the earlier fundamental insights.
Original languageEnglish (US)
Pages (from-to)18770-18781
Number of pages12
JournalACS Applied Materials & Interfaces
Volume11
Issue number20
DOIs
StatePublished - May 2019

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): BAS/1/1323-01-01
Acknowledgements: This publication is based on work supported by the King Abdullah University of Science and Technology (KAUST). IP Baseline Funding (KAUST) BAS/1/1323-01-01 (WO, XM, KH, ATA, IP). Financial support by the Ministerium für Innovation,Wissenschaft und Forschung des Landes Nordrhein-Westfalen, the Regierende Bürgermeister von Berlin – Senatskanzlei Wissenschaft und Forschung, and the Bundesministerium für Bildung und Forschung, and the European Union through the EFRE program (ProFIT grant, contract no.: 10160255, 10160265, and 10160256) is gratefully acknowledged by AF. The authors gratefully acknowledge the possibility for an extensive use of the KAUST Solar Center infrastructure.

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